Golf club head

ABSTRACT

[Object] It is an object of the present invention to provide a golf club head being lightweight and having a high strength. 
     [Solving Means] A head  2  includes a face  4 , a sole  8 , and a crown  6 . The face  4  includes a face surface fs and a face back surface fr. A plurality of projections (A) are provided on the face back surface fr. The projections (A) are point-like in a planar view. An optional first direction and a second direction orthogonal to the first direction are defined in the planar view. Preferably, arrangement regularity of the projections (A) in the second direction is higher than arrangement regularity of the projections (A) in the first direction. Preferably, the first direction is a longitudinal direction; and the second direction is a lateral direction.

TECHNICAL FIELD

The present invention relates to a golf club head.

BACKGROUND ART

In respect of an improvement in a degree of freedom of design, a golfhead being more lightweight and having a high strength is required.

Japanese Patent Application Laid-Open No. 2012-95855 discloses a headhaving a face part with a thickness distribution. The face part includesa middle thick part, a toe-crown side thin-walled part provided on acrown side of the middle thick part on a toe side of the middle thickpart and having a small thickness, and a heel-sole side thin-walled partprovided on a sole side of the middle thick part on a heel side of themiddle thick part and having a small thickness. In the head, reboundperformance in an off center shot is improved by providing thethin-walled part on a peripheral part of a face.

CITATION LIST Patent Literature

Patent Literature 1: JP-A-2012-95855

SUMMARY OF INVENTION Technical Problem

It has been found that a structure different from the structure of theconventional technique can provide a face being lightweight and having ahigh strength.

It is an object of the present invention to provide a golf club headbeing lightweight and having a high strength.

Solution to Problem

A golf club head of the present invention includes a face, a sole, and acrown. The face includes a face surface and a face back surface. Aplurality of projections (A) are provided on the face back surface. Theprojections (A) are point-like in a planar view.

An optional first direction and a second direction orthogonal to thefirst direction are defined in the planar view. Preferably, arrangementregularity of the projections (A) in the second direction is higher thanarrangement regularity of the projections (A) in the first direction.

Preferably, the first direction is a longitudinal direction; and thesecond direction is a lateral direction.

An area of each of the projections (A) in the planar view is defined asMa. Preferably, the two or more kinds of projections (A) have areas Masubstantially different from each other.

Preferably, the projections (A) include a projection (A1) of which thearea Ma is an area Ma1, a projection (A2) of which the area Ma is anarea Ma2, and a projection (A3) of which the area Ma is an area Ma3.Preferably, the area Ma1 is greater than the area Ma2. Preferably, thearea Ma2 is greater than the area Ma3. Preferably, the projection (A2)is disposed on a face peripheral side with respect to the projection(A1) in the first direction. Preferably, the projection (A3) is disposedon a face peripheral side with respect to the projection (A2) in thefirst direction.

A longitudinal distance between a periphery of the face back surface andthe projection (A1) is defined as a1. A longitudinal distance betweenthe periphery of the face back surface and the projection (A2) isdefined as a2. A longitudinal distance between the periphery of the faceback surface and the projection (A3) is defined as a3. An average valueof the distances a1 is defined as Av1. An average value of the distancesa2 is defined as Av2. An average value of the distances a3 is defined asAv3. Preferably, the average value Av1 is greater than the average valueAv2. Preferably, the average value Av2 is greater than the average valueAv3.

Preferably, an area Ma of each of the projections (A) is 3 mm² orgreater and 40 mm² or less in the planar view. Preferably, a height Haof each of the projections (A) is 0.03 mm or greater and 0.2 mm or less.

Preferably, a middle projection arrangement region including a face backsurface center is present as one of the projection arrangement regions.Preferably, arrangement regularity in the second direction is higherthan arrangement regularity in the first direction in the middleprojection arrangement region.

Preferably, the head is manufactured by joining a face member andanother member. Preferably, the face member is manufactured by forging.Preferably, the forging includes a preceding forging step and asubsequent forging step. Preferably, projections (B) higher than theprojections (A) are formed on the face back surface in the precedingforging step. Preferably, the projections (A) are formed by crushing theprojections (B) in the subsequent forging step.

Advantageous Effects of Invention

A golf club head being lightweight and having a high strength can beobtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a golf club head according to a firstembodiment of the present invention;

FIG. 2 is an exploded perspective view of the head of FIG. 1;

FIG. 3 is a plan view of a back surface of a face member, andprojections (A) are omitted in FIG. 3;

FIG. 4 is a cross-sectional view taken along line F4-F4 of FIG. 3; FIG.5 is a plan view of the back surface of the face member;

FIGS. 6( a), 6 (b), and 6(c) are plan views showing the shapes of theprojections (A);

FIG. 7 is a plan view for describing arrangement regularity;

FIG. 8 is a plan view of a face back surface according to a secondembodiment;

FIG. 9 is a plan view of a face back surface according to a thirdembodiment;

FIG. 10 is a plan view of a face back surface according to a fourthembodiment;

FIG. 11 is a plan view of a face back surface according to a fifthembodiment; and

FIG. 12 is a plan view of a face back surface according to a sixthembodiment.

DESCRIPTION OF EMBODIMENTS

The present invention will be described below in detail based onpreferred embodiments with appropriate reference to the drawings.

FIG. 1 is a perspective view of a golf club head 2 according to a firstembodiment of the present invention.

The head 2 includes a face 4, a crown 6, a sole 8, and a hosel 10. Theface 4 includes a face surface fs. The face surface fs is a hittingsurface. The crown 6 extends toward the back of the head from the upperedge of the face 4. The sole 8 extends toward the back of the head fromthe lower edge of the face 4. The head 2 is hollow. The head 2 is a woodtype golf club head.

FIG. 2 is an exploded perspective view of the head 2. The head 2 has afour-piece structure. Members constituting the head 2 are a face memberFp1, a sole member Sp1, a crown member Cp1, and a hosel member Hp1. Thehead 2 is manufactured by welding these members.

FIG. 3 is a plan view showing a back surface fr of the face member Fp1.FIG. 4 is a cross-sectional view taken along line F4-F4 of FIG. 3. Asdescribed later, a plurality of projections (A) are formed on the backsurface fr. However, these projections (A) are omitted in FIGS. 3 and 4.

The face member Fp1 constitutes the whole face 4. Furthermore, the facemember Fp1 includes a backward extending part Fp2 (see FIG. 4). Thebackward extending part Fp2 constitutes a part of the crown 6. Thebackward extending part Fp2 constitutes a part of the sole 8. The facemember Fp1 including the backward extending part Fp2 is also referred toas a cup face. A boundary k1 between the face member Fp1 and the otherportion is shown by a two-dot chain line in FIG. 1. The boundary k1 isnot visually recognized in the completed coated head 2.

The hosel 10 includes a shaft hole 12 to which a shaft is attached. Theshaft which is not shown is inserted into the shaft hole 12. Althoughnot shown in the figures, the shaft hole 12 has a center axis line Z1.The center axis line Z1 coincides with a shaft axis line of a golf clubincluding the head 2.

In the present application, a base perpendicular plane, a face-backdirection, and a toe-heel direction are defined. A state where thecenter axis line Z1 is included in a plane P1 perpendicular to a levelsurface H and the head 2 is placed at a predetermined lie angle and realloft angle on the level surface H is defined as a base state. The planeP1 is defined as a base perpendicular plane. The predetermined lie angleand real loft angle are described in, for example, a product catalog.

In the present application, the toe-heel direction is a direction of anintersection line between the base perpendicular plane and the levelsurface H.

In the present application, the face-back direction is a directionperpendicular to the toe-heel direction and parallel to the levelsurface H.

In the present application, a face center is defined. On the facesurface, a maximum width Wx in the toe-heel direction is determined.Furthermore, a middle position Px of the maximum width Wx in thetoe-heel direction is determined. At the position Px, a middle point Pyof the face surface in an up-down direction is determined. The point Pyis defined as the face center.

In the present application, an up-down direction is defined. The up-downdirection is a direction perpendicular to the face-back direction andperpendicular to the toe-heel direction.

In the present application, a longitudinal direction Dy is defined (seeFIG. 3). The longitudinal direction Dy is a direction of a projectionstraight line obtained by projecting a straight line drawn in theup-down direction onto a specific plane Ps (see FIG. 4). The specificplane Ps is a plane perpendicular to a straight line LN (describedlater).

In the present application, a lateral direction Dx is defined (see FIG.3). The lateral direction Dx is a direction on the specific plane Ps,and perpendicular to the longitudinal direction Dy. The lateraldirection Dx is equal to the toe-heel direction.

In the present application, a first direction D1 and a second directionD2 are defined. The first direction D1 and the second direction D2 aredirections on the specific plane Ps. The first direction D1 may be anydirection. The second direction D2 is orthogonal to the first directionD1. The longitudinal direction Dy is an example of the first directionD1. The lateral direction Dx is an example of the second direction D2.

In the present application, the disposition and areas of projections onthe face back surface fr are estimated in a planar view. The planar viewmeans a projection image Psi to the specific plane Ps.

In the projection to the specific plane Ps, the projection direction isa direction of a face normal line (described later).

In the present application, a face back surface center CR is defined.The straight line LN in FIG. 4 is a normal line of the face surface fspassing through a face center CF. An intersection point between thenormal line LN and the face back surface fr is the face back surfacecenter.

In the present application, the direction of the straight line LN isdefined as the direction of the face normal line.

The face member Fp1 may be divided into a plurality of regions based ona face thickness TF. As shown in FIG. 3, in the face back surface fr,division lines are formed. These division lines can be recognizedvisually as ridge lines. In a cross-sectional view, the ridge line has aroundness. The whole face back surface fr smoothly continues. As shownin FIG. 3, the face back surface fr includes a region S, a region Bt, aregion Bh, a region Ct, a region Ch, a region Da, a region Db, a regionEt, and a region Eh. Regions other than these regions are transitionregions having the thickness TF gradually changed.

The height of each of the projections (A) is not included in the facethickness TF.

In FIG. 3, hatching is applied to only the region S. Hatching is omittedin the other regions.

The region S is located in a middle part of the face 4. The region Sincludes a face center position. In other words, the region S includesthe face back surface center.

The region Bt is located below the region S. The region Bt is located ona toe side with respect to the face center. The region Bt is locatedbelow the face center.

The region Bh is located above the region S. The region Bh is located ona heel side with respect to the face center. The region Bh is locatedabove the face center.

The region Ct is located on a toe side with respect to the region S. Theregion Ct is located on a toe side with respect to the face, center. Theregion Ct includes a face center up-down position. The face centerup-down position is a position of the face center in the up-downdirection.

The region Ch is located on a heel side with respect to the region S.The region Ch is located on a heel side with respect to the face center.The region Ch includes the face center up-down position.

The region Da is located above the region S. The region Da is locatedabove the face center. The region Da includes a face center right-leftposition. The face center right-left position is a position of the facecenter in the toe-heel direction.

The region Db is located below the region S. The region Db is locatedbelow the face center. The region Db includes the face center right-leftposition.

The center of gravity of the region Et is located on a toe side withrespect to the region S. The region Et is located on a toe side withrespect to the face center. The region Et does not include the facecenter up-down position. The region Et does not include the face centerright-left position. The center of gravity of the region Et is locatedabove the center of gravity of the region Ct.

The center of gravity of the region Eh is located on a heel side withrespect to the region S. The region Eh is located on a heel side withrespect to the face center. The region Eh does not include the facecenter up-down position. The region Eh does not include the face centerright-left position. The center of gravity of the region Eh is locatedbelow the center of gravity of the region Ch.

In the present embodiment, the thickness TF of each region is asfollows.

-   -   region S: 3.3 mm or greater and 3.5 mm or less    -   region Bt: 2.5 mm or greater and 2.7 mm or less    -   region Bh: 2.5 mm or greater and 2.7 mm or less    -   region Ct: 2.4 mm or greater and 2.6 mm or less    -   region Ch: 2.4 mm or greater and 2.6 mm or less    -   region Da: 2.1 mm or greater and 2.3 mm or less    -   region Db: 2.1 mm or greater and 2.3 mm or less    -   region Et: 2.0 mm or greater and 2.2 mm or less    -   region Eh: 2.0 mm or greater and 2.2 mm or less

These regions are common in all embodiments which will be describedlater.

The difference between the maximum value and the minimum value of thethickness TF in each region is preferably equal to or less than 0.15 mm,and more preferably equal to or less than 0.1 mm.

The region S is a maximum thickness region Tm. If the maximum value ofthe face thickness TF is defined as Tmax (mm), the maximum thicknessregion Tm means a region in which the face thickness TF is equal to orgreater than [Tmax−0.2] mm. The face thickness TF is a thickness in thedirection of the face normal line.

The face back surface fr has at least a projection arrangement region.The projection arrangement region has two or more projections (A). Inthe embodiment of FIG. 5, the projection arrangement regions are theregion S, the region Ct, the region Ch, the region Et, and the regionEh.

As shown in FIG. 5, a plurality of projections (A) are arranged on theface back surface fr. The plurality of projections (A) are arranged ineach of the longitudinal direction Dy and the lateral direction Dx.

In the present application, an area of each of the projections (A) inthe planar view is defined as Ma. The two or more kinds of projections(A) having the areas Ma substantially different from each other areprovided on the face back surface fr. In the embodiment of FIG. 5, thethree kinds of projections (A) having the areas Ma substantiallydifferent from each other are provided. The phrase “substantiallydifferent” means that the difference between the areas Ma is equal to orgreater than 5%.

In the embodiment of FIG. 5, the three kinds of projections (A) includea projection (A1), a projection (A2), and a projection (A3). The area Maof the projection (A1) is Ma1. The area Ma of the projection (A2) isMa2. The area Ma of the projection (A3) is Ma3. The area Ma1, the areaMa2, and the area Ma3 are substantially different.

In the drawings of the present application, each of the projections (A)is shown by reference character Ta. In the drawings of the presentapplication, the projection (A1) is shown by reference character Ta1. Inthe drawings of the present application, the projection (A2) is shown byreference character Ta2. In the drawings of the present application, theprojection (A3) is shown by reference character Ta3.

Stress acting on the face is likely to be dispersed at random byproviding the two or more kinds of projections (A) having the areas Masubstantially different from each other. The dispersion of the stresscan relieve stress concentration to improve a face strength.

In the planar view, the projections (A) are point-like. FIGS. 6( a),6(b), and 6(c) show examples of point-like projections Ta. FIG. 6( a)shows a circular projection Ta. In the embodiment of FIG. 5, all theprojections Ta are circular. FIG. 6( b) shows an elliptical projectionTa. FIG. 6( c) shows an irregular projection Ta.

As shown in FIG. 6( c), a longest transversal line CL1 in an outline inthe planar view is determined. Furthermore, a transversal line CL2 whichis the longest among transversal lines perpendicular to the longesttransversal line is determined. A length of the transversal line CL1 isdefined as N1, and a length of the transversal line CL2 is defined asN2. In the case of the ellipse as shown in FIG. 6( b), the transversalline CL1 is a long axis, and the transversal line CL2 is a short axis.In the present application, the case where N1/N2 is equal to or lessthan 8 is defined to be point-like. In respect of improving the strengthof the face 4 while suppressing the mass of the projection Ta, N1/N2 ispreferably equal to or less than 5, more preferably equal to or lessthan 2, and still more preferably equal to or less than 1.5. N1/N2 isequal to or greater than 1. In the case of the circle, N1/N2 is 1.

Examples of the shape of the projection Ta in the planar view include aregular polygon as well as the above-mentioned circle and ellipse.Examples of the regular polygon include a square, a regular pentagon,and a regular hexagon. In respect of equally dispersing the stressacting on the face 4, the shape is preferably the circle.

[Effects of Projections (A)]

The projections (A) are point-like, and thereby the strength of the facecan be improved without thickening the whole face. The plurality ofprojections (A) are dispersively disposed, and thereby the face strengthcan be improved in a wide range without thickening the whole face. Thepoint-like projections (A) can be disposed at positions where animprovement in the strength is required, and thereby the degree offreedom of design of the face is improved. Therefore, a face 4 beinglightweight and having a high strength can be obtained. The point-likeprojections (A) are suitable for obtaining a strength improvement effect(described later) caused by forging.

In the present application, the arrangement regularity of theprojections (A) is defined. FIG. 7 is a view for describing thearrangement regularity. Herein, the case where the first direction D1 isthe longitudinal direction Dy and the second direction D2 is the lateraldirection Dx is described. The arrangement regularity is estimated inthe planar view.

In order to determine the arrangement regularity, a lateral directionline Lx and a longitudinal direction line Ly are considered. The lateraldirection line Lx is a straight line extending in the lateral directionDx. The longitudinal direction line Ly is a straight line extending inthe longitudinal direction Dy. In FIG. 7, a lateral direction line Lx1,a lateral direction line Lx2, and a lateral direction line Lx3 aredetermined as the lateral direction line Lx. In FIG. 7, a longitudinaldirection line Ly1, a longitudinal direction line Ly2, and alongitudinal direction line Ly3 are determined as the longitudinaldirection line Ly.

In the embodiment of FIG. 7, ten projections Ta are disposed. That is, aprojection 102, a projection 104, a projection 106, a projection 108, aprojection 110, a projection 112, a projection 114, a projection 116, aprojection 118, and a projection 120 are disposed.

The projection 102, the projection 104, and the projection 106 intersectwith a first lateral direction line Lx1. The projection 108, theprojection 110, and the projection 112 intersect with a second lateraldirection line Lx1. The projection 114, the projection 116, and theprojection 118 intersect with a third lateral direction line Lx1.

The projection 106, the projection 112, and the projection 118 intersectwith a first longitudinal direction line Ly1. The projection 104, theprojection 110, and the projection 116 intersect with a firstlongitudinal direction line Ly2. The projection 102, the projection 108,and the projection 114 intersect with a third longitudinal directionline Ly3.

A center of figure of the projection Ta is shown by reference charactergt in FIG. 7. A distance between the center of figure gt of theprojection Ta and the lateral direction line Lx is shown by adouble-headed arrow xd in FIG. 7. The lateral direction line Lxintersects with the two or more projections Ta. The number of thelateral direction line Lx which intersects with one projection Ta isone. In the embodiment of FIG. 7, each of the three lateral directionlines Lx intersects with the three projections Ta.

The projection Ta intersecting with the lateral direction line Lx is ameasurement target for the distance xd. However, the projection Ta whichdoes not intersect with the lateral direction line Lx may also beassumed. As shown in FIG. 7, the projection 120 which does not intersectwith the lateral direction line Lx is also a measurement target for thedistance xd. The distance xd is measured between the center of figure gtof the projection Ta and the lateral direction line Lx closest to thecenter of figure gt.

A distance between the center of figure gt of the projection Ta and thelongitudinal direction line Ly is shown by a double-headed arrow yd inFIG. 7. The longitudinal direction line Ly intersects with two or moreprojections Ta. The number of the longitudinal direction line Ly whichintersects with one projection Ta is one. In the embodiment of FIG. 7,each of the three longitudinal direction lines Ly intersects with threeprojections Ta.

The projection Ta intersecting with the longitudinal direction line Lyis a measurement target for the distance yd. Furthermore, as shown inFIG. 7, the projection 120 which does not intersect with thelongitudinal direction line Ly is also a measurement target for thedistance yd. The distance yd is measured between the center of figure gtof the projection Ta and the longitudinal direction line Ly (Ly3)closest to the center of figure gt.

As many lateral direction lines Lx and longitudinal direction lines Lysatisfying the above-mentioned condition as possible are determined. Anaverage value Xv1 of the distances xd and an average value Yv1 of thedistances yd are calculated. If a plurality of average values Xv1 can becalculated, the minimum value of the average values Xv1 is employed. Ifa plurality of average values Yv1 can be calculated, the minimum valueof the average values Yv1 is employed.

If Xv1 is smaller than Yv1, the difference of the following arrangementregularity is realized.

[Difference of Arrangement Regularity]: The arrangement regularity ofthe projections (A) in the lateral direction Dx is higher than thearrangement regularity of the projections (A) in the longitudinaldirection Dy.

Also if at least one lateral direction line Lx is present, and thelongitudinal direction line Ly is not present, the difference of thearrangement regularity is realized.

The difference of the arrangement regularity causes a projectionarrangement effect.

[Projection Arrangement Effect]

In order to describe the effect, a deformation in the toe-heel directionand a deformation in the up-down direction are defined. The deformationin the toe-heel direction in the present application means a deformationin which the fold by the deformation is generated in the up-downdirection. Meanwhile, the deformation in the up-down direction in thepresent application means a deformation in which the fold by adeformation is generated in the toe-heel direction.

The deformation in which the fold is generated in the up-down directionis less likely to occur by decreasing the arrangement regularity in thelongitudinal direction Dy. That is, the deformation in the toe-heeldirection is less likely to occur by decreasing the arrangementregularity in the longitudinal direction Dy.

The length of the face in the toe-heel direction is greater than thelength of the face in the up-down direction. For this reason, thedeformation in the toe-heel direction is likely to be greater than thedeformation in the up-down direction. The deformation in the toe-heeldirection can be effectively suppressed by decreasing the arrangementregularity in the longitudinal direction Dy. The face strength can beimproved by suppressing the excessive deformation.

Meanwhile, the deformation in the up-down direction is not excessivelysuppressed by increasing the arrangement regularity in the lateraldirection Dx. Therefore, the deterioration in rebound performance can besuppressed. Balance between the deformation in the toe-heel directionand the deformation in the up-down direction is favorable, and therebythe face strength can be optimized.

Selective suppression of a deformation in a predetermined direction maybe desired due to variation in hitting points, and design of a facethickness, or the like. In this case, the direction in which thesuppression of the deformation is desired can be set to the seconddirection. The arrangement regularity of the projections (A) in thesecond direction is set to be higher than the arrangement regularity ofthe projections (A) in the first direction. The deformation in thesecond direction can be effectively suppressed by the arrangement.

In the embodiment of FIG. 5, the number of the projections Ta(projections Ta1) intersecting with the first lateral direction line Lx1is X1. In the embodiment of FIG. 5, X1 is 10. In respect of improvingthe projection arrangement effect, X1 is preferably equal to or greaterthan 5, more preferably equal to or greater than 6, and still morepreferably equal to or greater than 7. In respect of suppressing theweight of the face 4, X1 is preferably equal to or less than 15, morepreferably equal to or less than 14, and still more preferably equal toor less than 13.

In the embodiment of FIG. 5, the number of the projections Ta(projections Ta1) intersecting with the second lateral direction lineLx2 is X2. In the embodiment of FIG. 5, X2 is 11. In respect ofimproving the projection arrangement effect, X2 is preferably equal toor greater than 5, more preferably equal to or greater than 6, and stillmore preferably equal to or greater than 7. In respect of suppressingthe weight of the face 4, X2 is preferably equal to or less than 15,more preferably equal to or less than 14, and still more preferablyequal to or less than 13.

In the embodiment of FIG. 5, the number of the projections Ta(projections Ta1) intersecting with the third lateral direction line Lx3is X3. In the embodiment of FIG. 5, X3 is 9. In respect of improving theprojection arrangement effect, X3 is preferably equal to or greater than5, more preferably equal to or greater than 6, and still more preferablyequal to or greater than 7. In respect of suppressing the weight of theface 4, X3 is preferably equal to or less than 15, more preferably equalto or less than 14, and still more preferably equal to or less than 13.

In the embodiment of FIG. 5, the arrangement regularity in the lateraldirection Dx is higher than the arrangement regularity in thelongitudinal direction Dy in the whole face back surface fr.

In the embodiment of FIG. 5, the arrangement regularity in the lateraldirection Dx is higher than the arrangement regularity in thelongitudinal direction Dy in the projection arrangement region S. Theprojection arrangement region S is a middle projection arrangementregion S including the face back surface center CR. Large stress acts onthe middle projection arrangement region S when a ball is hit. A portionon which the large stress acts can be selectively and effectivelyreinforced by applying the projection arrangement effect to the regionS.

In the embodiment of FIG. 5, the arrangement regularity in the lateraldirection Dx is higher than the arrangement regularity in thelongitudinal direction Dy in the projection arrangement region Ct. Theregion Ct is a toe side projection arrangement region located on a toeside with respect to the region S.

In the embodiment of FIG. 5, the arrangement regularity in the lateraldirection Dx is higher than the arrangement regularity in thelongitudinal direction Dy in the projection arrangement region Ch. Theregion Ch is a heel side projection arrangement region located on a heelside with respect to the region S.

In the embodiment of FIG. 5, the arrangement regularity in the lateraldirection Dx is higher than the arrangement regularity in thelongitudinal direction Dy in the projection arrangement region Et.

In at least one projection arrangement region, the difference of thearrangement regularity can be applied. The projection arrangement effectcan be applied to a desired projection arrangement region according tothe application. Therefore, a region requiring a strength can beselectively reinforced.

As shown in FIG. 5, in the longitudinal direction Dy (first directionD1), the projection Ta2 is disposed on a face peripheral side withrespect to the projection Ta1. The projection Ta3 is disposed on a faceperipheral side with respect to the projection Ta2. The position of theprojection Ta is estimated based on the center of figure gt. Alongitudinal distance between the periphery of the face back surface frand the projection Ta1 is defined as a1.

A longitudinal distance between the periphery of the face back surfacefr and the projection Ta2 is defined as a2. A longitudinal distancebetween the periphery of the face back surface fr and the projection Ta3is defined as a3. The longitudinal distance for each of the projectionsTa is measured.

The average value of the distances a1 is defined as Av1. The averagevalue of the distances a2 is defined as Av2. The average value of thedistances a3 is defined as Av3. The average value Av1 is greater thanthe average value Av2. The average value Av2 is greater than the averagevalue Av3.

The stress acting on the face 4 is comparatively large in the middlepart of the face 4. The stress acting on the face 4 is comparativelysmall in the peripheral part of the face 4. In light of this point, theprojection Ta of which the area Ma is comparatively small is disposed inthe peripheral part of the face 4, and the projection Ta of which thearea Ma is comparatively large is disposed in the middle part of theface 4. For this reason, the improvement in the face strength isachieved while the total volume of the projections (A) is suppressed.

Preferably, the area Ma of the projection (A) (projection Ta) is 3 mm²or greater and 40 mm² or less. In this range, the strength of the face 4can be effectively improved while the increase in the mass of the face 4is suppressed.

Preferably, the area Ma1 of the projection (A1) (projection Ta1) is 12mm² or greater and 40 mm² or less. In this range, the strength of theface 4 can be effectively improved while the increase in the mass of theface 4 is suppressed. The projection (A) having the area Ma differentfrom the area Ma1 can be easily provided by limiting the area Ma1 to therange.

Preferably, the area Ma2 of the projection (A2) (projection Ta2) is 6mm² or greater and 30 mm² or less. In this range, the strength of theface 4 can be effectively improved while the increase in the mass offace 4 is suppressed. The projection (A) having the area Ma differentfrom the area Ma2 can be easily provided by limiting the area Ma2 to therange.

Preferably, the area Ma3 of the projection (A3) (projection Ta3) is 3mm² or greater and 20 mm² or less. In this range, the strength of theface 4 can be effectively improved while the increase in the mass offace 4 is suppressed. The projection (A) having the area Ma differentfrom the area Ma3 can be easily provided by limiting the area Ma3 to therange.

In respect of improving an effect caused by the presence of theprojection Ta, the height Ha of the projection (A) is preferably equalto or greater than 0.03 mm, more preferably equal to or greater than0.05 mm, and still more preferably equal to or greater than 0.07 mm. Inrespect of reducing the mass of the face 4, the height Ha is preferablyequal to or less than 0.2 mm, more preferably equal to or less than 0.17mm, and still more preferably equal to or less than 0.15 mm.

FIG. 8 is a plan view showing a face back surface fr of a face memberFp20 according to a second embodiment. The plan view shows theabove-mentioned projection image Psi. Except for the projections Ta, theface member Fp20 is the same as the face member Fp1.

A projection occupation ratio Rs is considered in the face member Fp20.The ratio Rs of the middle projection arrangement region S is smallerthan the ratio Rs of the other region. The ratio Rs of the region S issmaller than the ratio Rs of the region Et. The ratio Rs of the region Sis smaller than the ratio Rs of the region Ct. The ratio Rs of theregion S is smaller than the ratio Rs of the region Eh. The ratio Rs ofthe region S is smaller than the ratio Rs of the region Ch. The ratio Rsis a ratio of the total area of the projections (A) to the area of theentire region. The ratio Rs is determined in the planar view.

In the face, the projection occupation ratio Rs of a face middle part isdecreased, and the projection occupation ratio Rs of a face peripheralpart is increased. Since the hardness of the peripheral part is furtherimproved, the thickness of the peripheral part can be decreased.Therefore, the whole face 4 is likely to bend, which can provide theenlargement of a sweet area.

FIG. 9 is a plan view showing a face back surface fr of a face memberFp30 according to a third embodiment. The plan view shows theabove-mentioned projection image Psi. Except for projections Ta, theface member Fp30 is the same as the face member Fp1.

In the face member Fp30, the projection occupation ratio Rs of a middleprojection arrangement region S is greater than the ratios Rs of theother regions. The ratio Rs of the region S is greater than the ratio Rsof the region Et. The ratio Rs of the region S is greater than the ratioRs of the region Ct. The ratio Rs of the region S is greater than theratio Rs of the region Eh. The ratio Rs of the region S is greater thanthe ratio Rs of the region Ch.

In the face, the projection occupation ratio Rs of a face middle part isincreased. Since the hardness of the middle part is further improved,the thickness of the middle part can be decreased. Therefore, thebending of the face 4 when a ball is hit with the middle part isincreased. For this reason, rebound performance when the ball is hitwith the face middle part is improved, which can provide an increase inthe maximum value of a coefficient of restitution. A maximum flightdistance can be increased by the increase.

FIG. 10 is a plan view showing a face back surface fr of a face memberFp40 according to a fourth embodiment. The plan view shows theabove-mentioned projection image Psi. Except for the projections Ta, theface member Fp40 is the same as the face member Fp1.

In the embodiment of FIG. 10, the arrangement regularity of theprojections (A) in a second direction D2 is higher than the arrangementregularity of the projections (A) in a first direction D1. The seconddirection D2 is inclined so as to be an upper side toward a toe side. Anangle between a lateral direction Dx and the second direction D2 isshown by a double-headed arrow θ1 in FIG. 10.

Usually, a golfer has variation in hitting points. The golfer's hittingpoints tend to be distributed between the upper side of a toe and thelower side of a heel. The arrangement of the projections (A) is adaptedfor the distribution of the hitting points by inclining the seconddirection D2 with respect to the lateral direction Dx. For this reason,the projection arrangement effect can be further improved. In light ofthe distribution of the hitting points, the lower limit of the angle θ1is preferably equal to or greater than 10 degrees, and more preferablyequal to or greater than 15 degrees. The upper limit of the angle θ1 ispreferably equal to or less than 50 degrees, and more preferably equalto or less than 45 degrees.

FIG. 11 is a plan view showing a face back surface fr of a face memberFp50 according to a fifth embodiment. The plan view shows theabove-mentioned projection image Psi. Except for the projections Ta, theface member Fp50 is the same as the face member Fp1.

In the embodiment of FIG. 11, a projection Ta2 is disposed betweenprojections Ta1. The area Ma2 of the projection Ta2 is smaller than thearea Ma1 of the projection Ta1. The projection occupation ratio Rs iseffectively improved by the disposition. In respect of improving theprojection occupation ratio Rs, Ma2/Ma1 is preferably equal to or lessthan 0.3, and more preferably equal to or less than 0.2. In respect ofpreventing Ma2 from being too small, Ma2/Ma1 is preferably equal to orgreater than 0.02, and more preferably equal to or greater than 0.05.

FIG. 12 is a plan view showing a face back surface fr of a face memberFp60 according to a sixth embodiment. The plan view shows theabove-mentioned projection image Psi. Except for the projections Ta, theface member Fp60 is the same as the face member Fp1.

In the embodiment of FIG. 12, the projection Ta has an ellipse shape.The long axis of the ellipse is substantially parallel to a lateraldirection Dx. In other words, the absolute value of an angle between thelong axis of the ellipse and the lateral direction Dx is equal to orless than 10 degrees. The projection Ta may not have the ellipse shape,and may have a shape shown in FIG. 6( c), for example. The absolutevalue of an angle between the longest transversal line CL1 and thelateral direction Dx is preferably equal to or less than 10 degrees. Theprojection arrangement effect can be further improved by theconstitution.

The volume of the head is not limited. The present invention iseffective when a face area is large. In this respect, the volume of thehead is preferably equal to or greater than 400 cc, more preferablyequal to or greater than 420 cc, and still more preferably equal to orgreater than 440 cc. In respect of observing the rules for the golfclub, the volume of the head is preferably equal to or less than 470 cc,and more preferably equal to or less than 460 cc.

The weight of the head is not limited. In respect of a swing balance,the weight of the head is preferably equal to or greater than 175 g,more preferably equal to or greater than 180 g, and still morepreferably equal to or greater than 185 g. In respect of the swingbalance, the weight of the head is preferably equal to or less than 205g, more preferably equal to or less than 200 g, and still morepreferably equal to or less than 195 g.

A method for manufacturing the head is not limited. Usually, a hollowhead is manufactured by joining two or more members. A method formanufacturing the members constituting the head is not limited. Examplesof the method include casting, forging, and press forming.

A method for manufacturing the face member Fp is not limited. Examplesof the method include casting, forging, and press forming. However, theforging is preferable as described later. A method for forming theprojections (A) is not limited. The projections (A) may be formedsimultaneously with the formation of the face member Fp, and process forforming the projections (A) may be performed after the formation of theface member Fp. Examples of the process include cutting by NC process,and chemical milling. As described later, the projections (A) arepreferably formed by forging the face member Fp.

The structure of the head is not limited. Examples of the structure ofthe head include a two-piece structure in which two members eachintegrally formed are joined, a three-piece structure in which threemembers each integrally formed are joined, and a four-piece structure inwhich four members each integrally formed are joined. The head 2 has thefour-piece structure.

[Manufacture of Face Member Fp1]

Preferably, the face member Fp1 is manufactured by forging. If theprojection (B) is crushed to form the projection (A), the forging numberof the face member Fp1 is multiple. For example, the forging number is 2or greater and 4 or less. In respect of productivity, the forging numberis preferably 2 or 3, and more preferably 2.

Generally, the first forging is also referred to as rough forging.Generally, the last forging is also referred to as main forging.

A plurality of forgings include a preceding forging step and asubsequent forging step. The subsequent forging step is performed afterthe preceding forging step. If the forging number is 2, the firstforging is the preceding forging step, and the second forging is thesubsequent forging step. If the forging number is equal to or greaterthan 3, it is preferable that the last forging is the subsequent forgingstep and the forging immediately prior to the last forging is thepreceding forging step.

The forging may be cold forging or hot forging. In respect of theimprovement in the strength caused by the densification of thestructure, the hot forging is preferable.

In the manufacture of the face member Fp1, in the preceding forgingstep, the approximate shape of the face member Fp1 is formed, and theprojection (B) is formed. The projection (B) is higher than theprojection (A). The projection (B) is crushed in the subsequent forgingstep. The crushed projection (B) constitutes the projection (A).

The projection (B) is crushed to form the projection (A), and therebydistortion is generated in metal crystal grains to producerecrystallization. The metal structure is densified by therecrystallization. The distortion can be generated by the crushing, tocause work hardening. The projection (B) is crushed to form theprojection (A), and thereby the strength of the face member Fp1 can beimproved.

Although the projection (B) is crushed, the projection (B) is notcompletely crushed, and the projection (A) remains. Therefore, an effectcaused by the crushing is obtained. At the same time, the formation ofthe projection (A) is also achieved.

The height of the projection (B) is defined as Hb. The height of theprojection (A) is defined as Ha. In respect of increasing thedeformation amount of the projection (B) to improve the strength of theface member Fp1, Hb/Ha is preferably equal to or greater than 1.5, morepreferably equal to or greater than 2, and still more preferably equalto or greater than 3. In respect of suppressing excessive crushingdeformation, Hb/Ha is preferably equal to or less than 15, morepreferably equal to or less than 12, and still more preferably equal toor less than 10.

In respect of obtaining moderate crushing deformation, the lower limitof the height Hb is preferably equal to or greater than 0.2 mm, and morepreferably equal to or greater than 0.3 mm. The upper limit of theheight Hb is preferably equal to or less than 1.5 mm, and morepreferably equal to or less than 1.2 mm.

The area of the projection (B) in the planar view is defined as My. Thearea My is smaller than the area Ma. The area Ma of the projection (A)is made to be greater than the area My by the crushing. In respect ofincreasing the deformation amount of the projection (B) to improve thestrength of the face member Fp1, Ma/My is preferably equal to or greaterthan 1.2, more preferably equal to or greater than 1.5, and still morepreferably equal to or greater than 2. In respect of suppressingexcessive crushing deformation, Ma/My is preferably equal to or lessthan 20, more preferably equal to or less than 15, and still morepreferably equal to or less than 12.

In respect of obtaining moderate crushing deformation, the followingitems (a) and/or (b) are/is preferable:

(a) the area My of the projection (B) for forming the projection (A) isgreater as the area Ma of the projection (A) is larger; and

(b) the height Hb of the projection (B) for forming the projection (A)is greater as the area Ma of the projection (A) is larger.

Example

Hereinafter, the effects of the present invention will be clarified byExample. However, the present invention should not be interpreted in alimited way based on the description of the Example.

Example

A face member Fp1, a sole member Sp1, a crown member Cp1, and a hoselmember Hp1 as shown in FIG. 2 were obtained by forging. A titanium alloywas used as a material for all the members. The material of the facemember Fp1 was “Super-TIX 51AF” (trade name) manufactured by NIPPONSTEEL & SUMITOMO METAL CORPORATION.

The forging number of the face member Fp1 was set to 2. The face memberFp1 was manufactured by a preceding forging step and a subsequentforging step. Both the preceding forging step and the subsequent forgingstep were hot forging. A round bar as a material was subjected to thepreceding forging step in a state where the round bar was set in apreceding forging mold. A preceding forged molded body was obtained inthe preceding forging step. The outer shape of the preceding forgedmolded body was substantially the same as the outer shape of the facemember Fp1 as a last molded body. The preceding forged molded body hadprojections (B). The positions and number of the projections (B) weremade the same as the positions and number of the projections (A) shownin FIG. 5.

The projections (B) included a projection (B1) of which the height Hbwas Hb1, a projection (B2) of which the height Hb was Hb2, and aprojection (B3) of which the height Hb was Hb3. The height Hb1 wasgreater than the height Hb2. The height Hb2 was greater than the heightHb3. The height Hb1 was set to 1 mm. The height Hb2 was set to 0.4 mm.The height Hb3 was set to 0.3 mm. The preceding forged molded body wassubjected to the subsequent forging step in a state where the precedingforged molded body was set in a subsequent forging mold. A subsequentforged molded body (face member Fp1 shown in FIG. 5) was obtained in thesubsequent forging step. The subsequent forged molded body had aprojection (A1), a projection (A2), and a projection (A3).

The projection (B1) was crushed to form the projection (A1). Theprojection (B2) was crushed to form the projection (A2). The projection(B3) was crushed to form the projection (A3).

The area Ma1 of the projection (A1) was 15 mm². The height Ha1 of theprojection (A1) was 0.1 mm. The area Ma2 of the projection (A2) was 12mm². The height Ha2 of the projection (A2) was 0.1 mm. The area Ma3 ofthe projection (A3) was 9 mm². The height Ha3 of the projection (A3) was0.1 mm.

The face member Fp1 and the other members were welded to obtain a headof Example as shown in FIG. 1. A 46-inch golf club was produced by usingthe head.

Comparative Example

A face member having no projection (A) was produced by changing aforging mold. In the face member, a face thickness was added as comparedwith Example. The face thickness was added to each of regions shown inFIG. 3. The additional thickness was made the same as the height of theprojection (A) which was present in each of the regions. A head and agolf club of Comparative Example were obtained in the same manner as inExample except for the constitution.

Although Comparative Example had no projection (A), manufacturingconditions in Comparative Example were made the same as manufacturingconditions in Example. Forging conditions such as the forging number inComparative Example were also made the same as forging conditions inExample.

[Evaluation of Strength]

A swing robot was equipped with a golf club, and repeatedly hit acommercially available two-piece ball at a head speed of 54 m/s. Ahitting point was set to a face center. It was visually confirmedwhether cracks were generated on a face surface for every 100 hits.

In Example, the hitting number when the cracks were confirmed was 10400.In Comparative Example, the hitting number when the cracks wereconfirmed was 10500. Although the face of Example was more lightweightthan the face of Comparative Example, the face strength of Example wasequivalent to the face strength of Comparative Example.

INDUSTRIAL APPLICABILITY

The present invention can be applied to all golf club heads such as awood type head, a utility type head, a hybrid type head, and an irontype head.

REFERENCE SIGNS LIST

-   -   2 Head    -   4 Face    -   6 Crown    -   8 Sole    -   10 Hosel    -   12 Shaft hole    -   fs Face surface    -   fr Face back surface    -   Fp1, Fp20, Fp30, Fp40, Fp50, Fp60 Face members    -   Cp1 Crown member    -   Sp1 Sole member    -   Hp1 Hosel member    -   Ta Projection (A)    -   Ta1 Projection (A1)    -   Ta2 Projection (A2)    -   Ta3 Projection (A3)

1. A golf club head comprising: a face; a sole; and a crown, wherein theface includes a face surface and a face back surface; a plurality ofprojections (A) are provided on the face back surface; and theprojections (A) are point-like in a planar view.
 2. The golf club headaccording to claim 1, wherein if an optional first direction and asecond direction orthogonal to the first direction are defined in theplanar view, arrangement regularity of the projections (A) in the seconddirection is higher than arrangement regularity of the projections (A)in the first direction.
 3. The golf club head according to claim 2,wherein the first direction is a longitudinal direction; and the seconddirection is a lateral direction.
 4. The golf club head according toclaim 1, wherein if an area of each of the projections (A) in the planarview is defined as Ma, the two or more kinds of projections (A) haveareas Ma substantially different from each other.
 5. The golf club headaccording to claim 1, wherein the projections (A) include a projection(A1) of which the area Ma is an area Ma1, a projection (A2) of which thearea Ma is an area Ma2, and a projection (A3) of which the area Ma is anarea Ma3; the area Ma1 is greater than the area Ma2, and the area Ma2 isgreater than the area Ma3; the projection (A2) is disposed on a faceperipheral side with respect to the projection (A1) in the firstdirection; and the projection (A3) is disposed on a face peripheral sidewith respect to the projection (A2) in the first direction.
 6. The golfclub head according to claim 1, wherein the projections (A) include aprojection (A1) of which the area Ma is an area Ma1, a projection (A2)of which the area Ma is an area Ma2, and a projection (A3) of which thearea Ma is an area Ma3; the area Ma1 is greater than the area Ma2, andthe area Ma2 is greater than the area Ma3; if a longitudinal distancebetween a periphery of the face back surface and the projection (A1) isdefined as a1; a longitudinal distance between the periphery of the faceback surface and the projection (A2) is defined as a2; a longitudinaldistance between the periphery of the face back surface and theprojection (A3) is defined as a3; an average value of the distances a1is defined as Av1; an average value of the distances a2 is defined asAv2; and an average value of the distances a3 is defined as Av3, theaverage value Av1 is greater than the average value Av2; and the averagevalue Av2 is greater than the average value Av3.
 7. The golf club headaccording to claim 1, wherein an area Ma of each of the projections (A)is 3 mm² or greater and 40 mm² or less in the planar view; and a heightHa of each of the projections (A) is 0.03 mm or greater and 0.2 mm orless.
 8. The golf club head according to claim 1, wherein a plurality ofprojection arrangement regions are provided on the face back surface;and arrangement regularity in the second direction is higher thanarrangement regularity in the first direction in at least one of theprojection arrangement regions.
 9. The golf club head according to claim1, wherein a plurality of projection arrangement regions are provided onthe face back surface; a middle projection arrangement region includinga face back surface center is present as one of the projectionarrangement regions; and arrangement regularity in the second directionis higher than arrangement regularity in the first direction in themiddle projection arrangement region.
 10. The golf club head accordingto claim 1, wherein the golf club head is manufactured by joining a facemember and another member; the face member is manufactured by forging;the forging includes a preceding forging step and a subsequent forgingstep; projections (B) higher than the projections (A) are formed on theface back surface in the preceding forging step; and the projections (A)are formed by crushing the projections (B) in the subsequent forgingstep.
 11. The golf club head according to claim 2, wherein if an area ofeach of the projections (A) in the planar view is defined as Ma, the twoor more kinds of projections (A) have areas Ma substantially differentfrom each other.
 12. The golf club head according to claim 3, wherein ifan area of each of the projections (A) in the planar view is defined asMa, the two or more kinds of projections (A) have areas Ma substantiallydifferent from each other.
 13. The golf club head according to claim 2,wherein the projections (A) include a projection (A1) of which the areaMa is an area Ma1, a projection (A2) of which the area Ma is an areaMa2, and a projection (A3) of which the area Ma is an area Ma3; the areaMa1 is greater than the area Ma2, and the area Ma2 is greater than thearea Ma3; the projection (A2) is disposed on a face peripheral side withrespect to the projection (A1) in the first direction; and theprojection (A3) is disposed on a face peripheral side with respect tothe projection (A2) in the first direction.
 14. The golf club headaccording to claim 3, wherein the projections (A) include a projection(A1) of which the area Ma is an area Ma1, a projection (A2) of which thearea Ma is an area Ma2, and a projection (A3) of which the area Ma is anarea Ma3; the area Ma1 is greater than the area Ma2, and the area Ma2 isgreater than the area Ma3; the projection (A2) is disposed on a faceperipheral side with respect to the projection (A1) in the firstdirection; and the projection (A3) is disposed on a face peripheral sidewith respect to the projection (A2) in the first direction.
 15. The golfclub head according to claim 4, wherein the projections (A) include aprojection (A1) of which the area Ma is an area Ma1, a projection (A2)of which the area Ma is an area Ma2, and a projection (A3) of which thearea Ma is an area Ma3; the area Ma1 is greater than the area Ma2, andthe area Ma2 is greater than the area Ma3; the projection (A2) isdisposed on a face peripheral side with respect to the projection (A1)in the first direction; and the projection (A3) is disposed on a faceperipheral side with respect to the projection (A2) in the firstdirection.
 16. The golf club head according to claim 2, wherein theprojections (A) include a projection (A1) of which the area Ma is anarea Ma1, a projection (A2) of which the area Ma is an area Ma2, and aprojection (A3) of which the area Ma is an area Ma3; the area Ma1 isgreater than the area Ma2, and the area Ma2 is greater than the areaMa3; if a longitudinal distance between a periphery of the face backsurface and the projection (A1) is defined as a1; a longitudinaldistance between the periphery of the face back surface and theprojection (A2) is defined as a2; a longitudinal distance between theperiphery of the face back surface and the projection (A3) is defined asa3; an average value of the distances a1 is defined as Av1; an averagevalue of the distances a2 is defined as Av2; and an average value of thedistances a3 is defined as Av3, the average value Av1 is greater thanthe average value Av2; and the average value Av2 is greater than theaverage value Av3.
 17. The golf club head according to claim 3, whereinthe projections (A) include a projection (A1) of which the area Ma is anarea Ma1, a projection (A2) of which the area Ma is an area Ma2, and aprojection (A3) of which the area Ma is an area Ma3; the area Ma1 isgreater than the area Ma2, and the area Ma2 is greater than the areaMa3; if a longitudinal distance between a periphery of the face backsurface and the projection (A1) is defined as a1; a longitudinaldistance between the periphery of the face back surface and theprojection (A2) is defined as a2; a longitudinal distance between theperiphery of the face back surface and the projection (A3) is defined asa3; an average value of the distances a1 is defined as Av1; an averagevalue of the distances a2 is defined as Av2; and an average value of thedistances a3 is defined as Av3, the average value Av1 is greater thanthe average value Av2; and the average value Av2 is greater than theaverage value Av3.
 18. The golf club head according to claim 4, whereinthe projections (A) include a projection (A1) of which the area Ma is anarea Ma1, a projection (A2) of which the area Ma is an area Ma2, and aprojection (A3) of which the area Ma is an area Ma3; the area Ma1 isgreater than the area Ma2, and the area Ma2 is greater than the areaMa3; if a longitudinal distance between a periphery of the face backsurface and the projection (A1) is defined as a1; a longitudinaldistance between the periphery of the face back surface and theprojection (A2) is defined as a2; a longitudinal distance between theperiphery of the face back surface and the projection (A3) is defined asa3; an average value of the distances a1 is defined as Av1; an averagevalue of the distances a2 is defined as Av2; and an average value of thedistances a3 is defined as Av3, the average value Av1 is greater thanthe average value Av2; and the average value Av2 is greater than theaverage value Av3.
 19. The golf club head according to claim 5, whereinthe projections (A) include a projection (A1) of which the area Ma is anarea Ma1, a projection (A2) of which the area Ma is an area Ma2, and aprojection (A3) of which the area Ma is an area Ma3; the area Ma1 isgreater than the area Ma2, and the area Ma2 is greater than the areaMa3; if a longitudinal distance between a periphery of the face backsurface and the projection (A1) is defined as a1; a longitudinaldistance between the periphery of the face back surface and theprojection (A2) is defined as a2; a longitudinal distance between theperiphery of the face back surface and the projection (A3) is defined asa3; an average value of the distances a1 is defined as Av1; an averagevalue of the distances a2 is defined as Av2; and an average value of thedistances a3 is defined as Av3, the average value Av1 is greater thanthe average value Av2; and the average value Av2 is greater than theaverage value Av3.
 20. The golf club head according to claim 2, whereinan area Ma of each of the projections (A) is 3 mm² or greater and 40 mm²or less in the planar view; and a height Ha of each of the projections(A) is 0.03 mm or greater and 0.2 mm or less.